Gas-Phase Epoxidation of Propene with Hydrogen Peroxide Vapor

A study on the gas-phase epoxidation of propene with vapor hydrogen peroxide has been carried out. The main purpose was to understand the key factors in the reaction and the relationship between epoxidation of propene and decomposition of hydrogen peroxide, which is the main side reaction. The decomposition was highly influenced by the materials used, being higher in metals than in polytetrafluoroethylene (PTFE) and glass, and it was complete when the epoxidation catalyst, TS-1, was introduced in the system. However, when propene was added, the peroxide was preferentially used for the epoxidation, even with amounts of catalyst as small as 10 mg, reaching productivities of 10.5 kg_PO·kg_cat^–1·h^–1 for a gas hourly space velocity (GHSV) of 450 000 mL·g_cat^–1·h^–1. The hydrogen peroxide was converted completely in all the experiments conducted, with a selectivity to PO of around 40% for all peroxide concentrations. Finally, if concentrations of propene higher than the stoichiometrically required amounts were used, the selectivity to PO increased to almost 90%

Transfer of the Epoxidation of Soybean Oil from Batch to Flow Chemistry Guided by Cost and Environmental Issues

The simple transfer of established chemical production processes from batch to flow chemistry does not automatically result in more sustainable ones. Detailed process understanding and the motivation to scrutinize known process conditions are necessary factors for success. Although the focus is usually “only” on intensifying transport phenomena to operate under intrinsic kinetics, there is also a large intensification potential in chemistry under harsh conditions and in the specific design of flow processes. Such an understanding and proposed processes are required at an early stage of process design because decisions on the best-suited tools and parameters required to convert green engineering concepts into practice—typically with little chance of substantial changes later—are made during this period. Herein, we present a holistic and interdisciplinary process design approach that combines the concept of novel process windows with process modeling, simulation, and simplified cost and lifecycle assessment for the deliberate development of a cost-competitive and environmentally sustainable alternative to an existing production process for epoxidized soybean oil

Water and n‑Heptane Volume Fractions in a Rotor-Stator Spinning Disc Reactor

This paper presents the volume fractions of n-heptane and water measured in a rotor-stator spinning disc reactor. The volume fractions were measured using γ-ray tomography and photographic image analysis. The volume fractions were determined as a function of rotational disc speed, flow ratio, position in the reactor, and rotor material. In addition, the effect of the density difference between water and n-heptane was determined by dissolving potassium iodide in the water phase. Below a rotational disc speed of 75 rpm the volume fraction measured by tomography and photographic image analysis are within 10% deviation. For low rotational disc speeds, the n-heptane volume fraction decreases slightly with increasing rotational disc speed: the centrifugal force accelerates the larger n-heptane droplets to the center. At higher rotational disc speeds the droplets become smaller accordingly, the friction between the phases determines the flow, and the n-heptane volume fraction becomes equal to the n-heptane to total flow ratio. An increase in density difference from 0.31 to 0.79 kg dm^–3 did not influence the volume fractions

Design of a thick-walled screen for flow equalization in microstructured reactors

A systematic computational fluid dynamics (CFD) approach has been applied to design the geometry of the channels of a three-dimensional (thick-walled) screen comprising upstream and downstream sets of elongated channels positioned at an angle of 90° with respect to each other. Such a geometry of the thick-wall screen can effectively drop the ratio of the maximum flow velocity to mean flow velocity below 1.005 in a downstream microstructured reactor at low Reynolds numbers. In this approach the problem of flow equalization reduces to that of flow equalization in the first and second downstream channels of the thick-walled screen. In turn, this requires flow equalization in the corresponding cross-sections of the upstream channels. The validity of the proposed design method was assessed through a case study. The effect of different design parameters on the flow non-uniformity in the downstream channels has been established. The design equation is proposed to calculate the optimum values of the screen parameters. The CFD results on flow distribution were experimentally validated by Laser Doppler Anemometry measurements in the range of Reynolds numbers from 6 to 113. The measured flow non-uniformity in the separate reactor channels was below 2%